Since its introduction to the market in 1962, aromatic polycarbonate has become well known and accepted as a thermoplastic resin suitable for a wide variety of uses including injection molding, extrusion and film formation. The chemistry, synthesis, properties and applications of these polycarbonates are extensively discussed in Chemistry and Physics of Polycarbonates by Schnell, Interscience, 1964 and Polycarbonates by Christopher and Fox, Reinhold, 1962. Although polycarbonates being self-extinguishing have some inherent flame resistance, ever more demanding requirements of flame-resistance have spawned numerous attempts to increase this property. One approach has been to add substantial amounts of halogen, particularly bromine or chlorine, to polycarbonate compositions. The halogen can be carried by polycarbonate polymer chains such as described in U.S. Pat. Nos. 3,751,400 and 3,334,154 or by a monomeric compound as in U.S. Pat. No. 3,382,207. However, the presence of substantial amounts of halogen has been found to be detrimental to the properties of the polycarbonate, and numerous additives such as those found in U.S. Pat. Nos. 3,647,747 and 3,733,295 have been proposed to overcome those detrimental effects.
Flame retardant polycarbonate products are available in which no brominated or chlorinated flame retardant additives are included. However, fluorine containing compounds are included to provide flame retardancy. For example, US Published Patent Application No. 2007/0082995 in the name of Costanzi et al. discloses a thermoplastic halogen-free flame retardant composition containing at least a hypophosphorous acid metal salt as a halogen-free flame retardant agent, and at least an aromatic polycarbonate resin and/or its blends. The flame retardant composition may include additives and fillers, in particular, fluorine-containing ethylene polymers which exhibit a resin melt dropping preventing effect when the composition is fired. The disclosure of Costanzi et al. also refers to molded thermoplastic articles made by using the flame retardant composition.
JP 2008-143997 in the name of Hiromitsu et al. provides a polycarbonate resin composition which are said to be excellent in rigidity, self-tap strength, dimensional stability, flame retardancy, fluidity, and appearance, prepared by compounding 100 pts. wt. polycarbonate resin with 0.1-20 pts. wt. acrylonitrile/styrene copolymer, 0.1-30 pts. wt. polycarbonate olygomer, 10-25 pts. wt. phosphorus-containing flame retardant, 80-160 pts. wt. glass filler of a glass fiber/glass flake weight ratio in the range of 0.2-4.0, and 0.1-2.5 pts. wt. polyfluoroolefin-type polymer (component F). An optical component may be molded from the resin composition of Hiromitsu et al.
Yuichi et al. in JP 2005-206698, discloses a flame-retardant polycarbonate resin composition said to be excellent in wet-heat resistance and excellent in heat stability, processability, transparency, etc., and having flame retardancy improved without using any chlorine- or bromine-containing compound. The polycarbonate composition is prepared by formulating 100 pts. wt. polycarbonate containing 100 to 20 wt. % aromatic polycarbonate resin having a structural viscosity index N of 1.2 or higher with 0.001 to 5 pts. wt. flame retardant represented by formula (B-1) or formula (B-2).
In formula (B-1), m is an integer of 1 to 12; and M is an alkali metal or an alkaline earth metal; q is 2 when M is an alkali metal and is 1 when M is an alkaline earth metal. In formula (B-2), Rf is an optionally substituted perfluoroalkyl group having 2 to 12 carbon atoms in total; M′ is an alkali metal or an alkaline earth metal; and n is equal to the valence of M′.
U.S. Pat. No. 7,223,804 issued to An et al. describes a thermoplastic composition containing polycarbonate, an impact modifier having a pH of about 3 to about 7, and a flame retardant essentially free of bromine and chlorine.
Gallucci et al., in U.S. Pat. No. 7,259,201, provides a film, which contains greater than or equal to about 95 wt % thermoplastic resin, based on a total weight of the film, wherein the thermoplastic resin is selected from the group consisting of polyimide, polyetherimide, polyetherimide sulfone, and copolymers, reaction products, and combinations comprising at least one of those thermoplastic resins; and about 0.001 wt % to about 5.0 wt % of a fluoroalkyl sulfonate salt, based on the total weight of the film; wherein the film has a UL-94 rating of VTM-0 and further wherein less than or equal to 2,500 parts per million by weight of bromine is present.
JP 2004-043741 in the name of Manabu et al. describes a resin composition said to have high rigidity and flame retardancy, sufficient heat-resistance, excellent flowability and low mold-staining property which is made from (G) 60-97 mass % flame-retardant resin composition produced by compounding (D) 100 pts. mass of a resin composition composed of (A) 5-60 mass % graft copolymer produced by the graft polymerization of a monomer containing an aromatic alkenyl compound monomer (a) and/or a vinyl cyanide compound monomer (b) to a rubbery polymer (r), (B) 0-45 mass % polymer containing the monomer unit (a) and/or the monomer unit (b) and (C) 40-95 mass % polycarbonate resin with (E) 1-30 pts. mass of a phosphate-based flame-retardant and (F) 0.3-10 pts. mass of a red-phosphorus flame retardant and (H) 3-40 mass % fibrous filler.
Chiba et al., in U.S. Pat. No. 6,174,944, discloses a flame retardant polycarbonate resin composition and housings of the composition for electric and electronic instruments and appliances. The composition is said to have good fluidity and good moldability, can be molded into thin-wall moldings with good appearance. The composition of Chiba et al. contains additive components of a fibrous filler, a terpene resin, a composite rubber-based graft copolymer, a halogen-free phosphate compound and a polytetrafluoroethylene.
Therefore, a need continues to exist in the art for a polycarbonate with improved flame retardancy which do not include a halogenated flame retardant in the formulation.